1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/local_.R, R/with_.R
\name{local_}
\alias{local_}
\alias{with_}
\title{Create a new "with" or "local" function}
\usage{
local_(set, reset = set, envir = parent.frame(), new = TRUE, dots = FALSE)
with_(set, reset = set, envir = parent.frame(), new = TRUE)
}
\arguments{
\item{set}{\verb{[function(...)]}\cr Function used to set the state.
The function can have arbitrarily many arguments, they will be replicated
in the formals of the returned function.}
\item{reset}{\verb{[function(x)]}\cr Function used to reset the state.
The first argument can be named arbitrarily, further arguments with default
values, or a "dots" argument, are supported but not used: The function will
be called as \code{reset(old)}.}
\item{envir}{\verb{[environment]}\cr Environment of the returned function.}
\item{new}{\verb{[logical(1)]}\cr Replace the first argument of the \code{set} function
by \code{new}? Set to \code{FALSE} if the \code{set} function only has optional arguments.}
}
\value{
\verb{[function(new, code, ...)]} A function with at least two arguments,
\itemize{
\item \code{new}: New state to use
\item \code{code}: Code to run in that state.
}
If there are more arguments to the function passed in \code{set} they are
added to the returned function. If \code{set} does not have arguments,
or \code{new} is \code{FALSE}, the returned function does not have a \code{code} argument.
}
\description{
These are constructors for \code{with_...} or \code{local_...} functions.
They are only needed if you want to alter some global state which is not
covered by the existing \code{with_...} functions, see \link{withr}
for an overview.
}
\details{
The \code{with_...} functions reset the state immediately after the
\code{code} argument has been evaluated. The \code{local_...} functions
reset their arguments after they go out of scope, usually at the end of the
function body.
}
\examples{
with_(setwd)
global_stack <- list()
set_global_state <- function(state, msg = "Changing global state.") {
global_stack <- c(list(state), global_stack)
message(msg)
state
}
reset_global_state <- function(state) {
old_state <- global_stack[[1]]
global_stack <- global_stack[-1]
stopifnot(identical(state, old_state))
}
with_(set_global_state, reset_global_state)
}
\keyword{internal}
|
